DuckCorp Dico

Found one definition

1.                 From The Free On-line Dictionary of Computing (19 January 2023):
                   
   
   
                   
                     
   whack
      According to arch-hacker James Gosling, to "...modify a
      program with no idea whatsoever how it works." (See
      whacker.)  It is actually possible to do this in nontrivial
      circumstances if the change is small and well-defined and you
      are very good at glarking things from context.  As a trivial
      example, it is relatively easy to change all "stderr" writes
      to "stdout" writes in a piece of C filter code which remains
      otherwise mysterious.
      [Jargon File]